Get rid of a redundant argument DOWNSTREAM from VisiblePosition constructor call sites

Source/core/editing/SelectionController.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2012 Digia Plc. and/or its subsidiary(-ies)
  * Copyright (C) 2015 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
@@ skipping 139 matching lines @@
         LayoutPoint vPoint = view->rootFrameToContents(event.event().position());
         if (!extendSelection && selection().contains(vPoint)) {
             m_mouseDownWasSingleClickInSelection = true;
             return false;
         }
     }
 
     PositionWithAffinity eventPos = innerNode->layoutObject()->positionForPoint(event.localPoint());
     VisiblePosition visiblePos(Strategy::toPositionType(eventPos.position()), eventPos.affinity());
     if (visiblePos.isNull())
-        visiblePos = VisiblePosition(firstPositionInOrBeforeNode(innerNode), DOWNSTREAM);
+        visiblePos = VisiblePosition(firstPositionInOrBeforeNode(innerNode));
     PositionType pos = Strategy::toPositionType(visiblePos.deepEquivalent());
 
     VisibleSelection newSelection = selection().selection();
     TextGranularity granularity = CharacterGranularity;
 
     if (extendSelection && newSelection.isCaretOrRange()) {
         VisibleSelection selectionInUserSelectAll(expandSelectionToRespectUserSelectAll(innerNode, VisibleSelection(VisiblePosition(pos))));
         if (selectionInUserSelectAll.isRange()) {
             if (Strategy::selectionStart(selectionInUserSelectAll).compareTo(Strategy::selectionStart(newSelection)) < 0)
                 pos = Strategy::selectionStart(selectionInUserSelectAll);
@@ skipping 478 matching lines @@
     else
         m_selectionState = SelectionState::HaveNotStartedSelection;
 }
 
 FrameSelection& SelectionController::selection() const
 {
     return m_frame->selection();
 }
 
 } // namespace blink